class Solution:
    def __init__(self):
        self.__mapper = {1: 1, 2: 2}

    def climbStairs(self, n: int) -> int:
        dp = {1:1, 2:2}

        for i in range(3, n+1):
            dp[i] = dp[i-1] + dp[i-2]
        return dp[n]